Millersburg, Ohio — For Jacob Beachy, life moves along much as it always has. Every day, there are the 35 cows that need tending, as well as 90 acres of farmland. His is the life of an Amish farmer, in which family, work, and faith intertwine on one plot of Ohio land.

Yet across the street, on 60 acres that were once a farm, stands a sprawling new mansion, complete with a multidoor garage. A few years back, that land sold for $1.4 million.

“When we moved here in 1968, we thought we were in the sticks,” Mr. Beachy says, rocking in his living-room recliner. “All of this was working farms. It’s changed a lot.”

Indeed, for America’s Amish, much is changing. The Amish are, by one measure, the fastest-growing faith community in the US. Yet as their numbers grow, the land available to support the agrarian lifestyle that underpins their faith is shrinking, gobbled up by the encroachment of exurban mansions and their multidoor garages.

The result is, in some ways, a gradual redefinition of what it means to be Amish. Some in the younger generation are looking for new ways to make a living on smaller and smaller slices of land. Others are looking beyond the Amish heartland of Ohio, Pennsylvania, and Indiana, seeking more space in states such as Texas, Maine, and Montana.

In Ohio’s Amish country, centered in Holmes County about 80 miles south of Cleveland, these forces are reshaping a region where 42 percent of residents are Amish – the highest percentage of any part of the US. Amid these changes, Amish here are struggling to maintain the traditions they hold dear: establishing core values within the family through manual labor close to home.

The American Amish population has boomed during the past few decades. A study released this summer by Ohio State University in Columbus found that the Amish are growing faster than any other faith-based group in the US, with 60 percent of all Amish settlements in the US founded since 1990.

According to the study, there are 456 settlements in the US and Canada – a number forecast to reach 1,000 by 2050. Likewise, the US Amish population – now at 251,000 –is estimated to grow to more than a million by 2050, the researchers add.

The most apparent reason for such rapid growth, experts say, is that Amish birthrates are high and the community emphasizes keeping children in the faith. About 90 percent of Amish children keep their family traditions intact, though many may temporarily stray as teens and young adults, says David Weaver-Zercher, a religion professor at Messiah College in Mechanicsburg, Pa.

In the Amish heartland, these demographics are clashing with geography, as Beachy can attest. “Amish will have to spread out,” Beachy says. “That’s why you see settlements all over – they are looking for farmland. You can’t buy a farm anymore to farm.”

With his own farm, Beachy is in an enviable position. “I’ll never find out what this farm is worth, because I’ll never sell it,” he says.

But the nascent Amish diaspora is not always about economics. Some families are moving to other areas of the country because they think parenting becomes more difficult in a larger, more populated area – even if it’s Amish, says Professor Weaver-Zercher.

For example, nearly 30,000 Amish live in the greater Holmes County settlement, which is the nation’s largest and spreads over five counties. (Amish “settlements” refer not to places with defined boundaries, but to regional communities where the majority of the population is Amish.)

“Some Amish parents are looking for more secluded places, not just from the English” – non-Amish – “but sometimes from other Amish teens, because they want more supervision over their young people,” says Weaver-Zercher, noting that larger settlements can make it easier for young people to engage in risky behavior – such as drug use or alcohol consumption – more anonymously.

“Instead of a community of 5,000 kids, you suddenly have one with 25 kids,” he adds. “At that level, the roughhousing activities will be more akin to what parents approve.”

These issues are particularly poignant for the Amish, given that most formally end their education after the eighth grade. The population boom – combined with the land crunch – is forcing more young people to search for work outside the family home, which means they will experience a world much different from the one their parents knew, says Weaver-Zercher.

On the good side, they will have more disposable income, which will translate to more savings. But working with non-Amish supervisors and co-workers means there will be challenges in maintaining the work ethic and values that have been traditionally taught on the family farm.

Ernie Hirschberger, a father of seven, says his oldest son asked for a car when he was 16 because he “wanted more freedom.” Four years later, that car now sits with a “for sale” sign outside Homestead Furniture, the custom furniture operation Mr. Hirschberger runs with his family and 35 employees in Mount Hope, Ohio.

Hirschberger is a symbol of the future of Amish entrepreneurs: He grew up on a farm, but he started making furniture 22 years ago and today his pieces can be found in all 50 states. His son, who has now embraced the Amish lifestyle, is a manager in the company’s finishing room.

“He’s still a work in progress. He needs to learn,” Hirschberger says.

Besides furniture, which is now a growth area for Amish business, Hirschberger says he is looking to bring new ideas to Holmes County, such as shrimp and fish farms or using hydroponics to grow herbs. He knows he can’t raise cows on his family plot of 10 acres, but he can help innovate new business models for Amish people.

“You can’t just pick up your horse and buggy and go to Cleveland and be a computer tech,” he says. “We just have to think of other things for the smaller plots of land.”

There are tangible benefits of staying in the settlements. The self-sufficiency of the Amish lifestyle, and its emphasis on community strength, meant the recession did not hit most Amish settlements as hard as it did the outside world. That economic security, Hirschberger says, is one reason more young people are deciding to follow in Amish traditions today than they did when he was coming of age.

“They say, ‘This is a good option for our kids,’ ” he says. “To grow up as Christians should and in this lifestyle is not a hindrance.”